There are different levels to these things. The number of SIM card slots or bands varying from model to model isn't that unusual. The average user just needs it to work. In fact, the SIM and band configuration differences have nothing to do with regional legal mimina — they have more to do with the standard practice and available systems in each region (for example, mmWave isn't widely deployed outside the US). The configurations aren't really "worse" in the same way as locking down browser access is worse. Phones have had regional variants going back ~forever for pretty mundane and benign reasons.

More importantly, if a user travels from one region to another, as long as they can use their phone in the place they arrive, having slightly non-optimal bands or a different SIM configuration doesn't matter. The fact that your phone is slightly different from the local model is not really a problem.

But having your charger vary across regions? That's a recipe for disaster. Not only is that another level of variance in your external casing, it impacts day-to-day use. When an American user travels to, say, France, or vice versa, and wants to buy a charger, or share one with someone else, having the same model of iPhone be incompatible would be a major frustration. It would be stupid to engineer a lightning AND USB-C version of the same device for each market.